The findings of multiple studies indicate that participation in Behavioral Couples Therapy (BCT) is associated with robust positive outcomes for drug-abusing patients and their partners, in terms of reduced substance use and improved relationship and family functioning. Yet, community-based treatment programs rarely offer BCT to incoming eligible patients. As reported by providers and administrators in a national survey of treatment programs in the U.S., BCT was viewed as prohibitively labor intensive, due in large measure to its standard conjoint delivery format (i.e., a couple treated by one or sometimes two providers). Given the public policy climate that is now emphasizing not only clinical effectiveness, but also economic accountability, an intervention's efficiency (i.e., the ratio of effectiveness to program resources used to provide the service) is a critical factor in decisions by treatment programs to adopt new interventions. Although BCT has well-proven efficacy, the consensus of providers and administrators is that BCT is not efficient. With these concerns in mind, we recently completed pilot project (i.e., a Stage IA/B study) with married or cohabiting drug-abusing patients and their partners examining the efficacy of an multi-couple group therapy version of BCT (G-BCT) compared to standard BCT (S-BCT), individual-based treatment (group and individual counseling) for the substance-abusing partner only, and multi-couple attention control treatment. Results indicated G-BCT yielded equivalent outcomes when compared to S-BCT, in terms of reduction in substance use and improved relationship adjustment, but was less costly to deliver and had superior cost-benefit and cost-effectiveness. Both G-BCT and S-BCT yielded better clinical and cost-outcomes than individual-based treatment or the attention control. Additionally, a subsequent small-scale dissemination pilot study indicated G-BCT was more likely to be used in community-based treatment programs than S-BCT. Thus, the objective of this proposed Stage II investigation is to conduct a randomized clinical trial to examine the clinical effectiveness, in terms of substance use, relationship functioning, and psychosocial adjustment, of Group BCT (G-BCT) versus (a) Standard BCT (S-BCT), (b) traditional Individual-Based Treatment (IBT), and (c) multi-couple Group Psychoeducational Attention Control Treatment (G-PACT), for 240 substance-abusing patients and their nonsubtance-abusing partners. Given the likely differences in cost of treatment delivery among the interventions, we will also examine the comparative cost-benefit and cost-effectiveness of the intervention packages.